Mercury switch relay



1941'- c. H. CARTWRIGHT ETAL 2,232,877

MERCURY SWITCH RELAY Filed April 14, 1958 s Sheets-Sheet 1 22 2 Carl [kl/307 1941- c. H. CARTWRIGHT ETAL 2,232,377

MERCURY SWITCH RELAY Filed April 14, 1938 3 Sheets-Sheet 2 I 1//////// Ill/l Cad 1941- c. H. CARTWRIGHT ETAL' 2,232,377

MERCURY SWITCH RELAY Filed April 14, 1938 3 Sheets-Sheet 3 Patented Feb. 25, 1941 I 1 2,232,877

UNITED STATES PATENT OFFICE mnwnar swrrcn RELAY Charles H. Cartwright and Carl B. Larson, Elkhart, Ind assignors to The Adiake Company, a corporation of Illinois v Application April 14, 1938, Serial No. 202,003 5 Claims. (01. 200-97) This invention relates broadly to mogul-Z placerth riseswithbecaelusepgt its buoyancy, to the top switches, for certain features or parts e s env o ats??? eee fleeuy iiif dol s? fuifi m m e eiiif wfieifi 32 it of mer more s s vention pe rtains to that type oi mercury switch placer is lowered by the action 0! the coil; in which spaced electrodes, together with a quan- Fig. is a horizontal sectional view taken on tity oi mercury and a magnetically responsive disthe line ll -lii of Fig. 8; and 1 smelt ms t its when ve we r w e assoc 10 a coil which controls the movement ofththe dlsmfid slo :hcerreuifi a relgzgregeshsowriiictfimig 10 Inner within the envelo to ch e e merw en 0 thro :ury level and thereby ca use the l ectrlcal cirbeing closed and a relatively i ns time n v l cult between the spaced electrodes to be closed wh gled he circuit hrough the switch is being th ular cope i ors lfi fie gi t c i to 8 name comm Certain preferred forms of the invention have 15 In seneral the objects oi the invention are been chosen for ill t atio and description. n to vide a time delay switch which, by slight compliance with Section 4888 of the Revised eh ee in physical structure and/or apportion- Stamtes, and the appended claims should be conment or parts during fabrication, can be made to s r d as b adly as the prior art will permit.

iulflll widely varying performance specifications; The men one which relatively chnptomumcture' i The switch mounting shown in Figs 1 to 3 is f gf gf ffig m a simple and inexpensive construction which not are hermetically sealed within the switch enpmvmea an mclent cult the velope; and one which is reliable in performance asg gg but also mwdsphydcal mmuon 25 33,3:g2 3331'1335- object, and advm The mounting for the switch, generally deslgchm nated 20'. comprises an L shaped plate 2i conwas r eizr efi o l iem l l ag ti t li: eting top and bottom pole plates 22 and 23, reso m which speetively. the latter having a downwardly exso m We a n mts s'h'i stztm sf sests l g isw e l ti c g e n a i s w taken on the menu!!! con telescope! over um switch a and over top and bottom pole sleeves 21 and 28,

as sw the being which are rigidly secured to the top and'bottom as me t is a plan view of the switch withits 232* 3 z g f f g'gi 5 fixi g moun ng;

Fla- 4 is an enlarged vertical sectional view of g by :2 :3 zg gz ga fi g g z sg 40 a back Contact switch em 5 us some 0! the the associated iron circuit, and whensoassembled 4o principles 01' this invention, the switch parts bem the bottom 01 the switch is supported on the hori- 3 shown in their normal position of rest when zonm flange o themate z I and the top 0! the the minted is deenergized' switch is slightly below the top of the sleeve 21,

Fig. 5 is a view showing the relationship of the so that it is amply protected from m1 dent a1 switch parts at the instant when the displacer blows is raised by the associated coll; 1 y

Fix. 61s a horizontal sectional view taken on the gzg i zg 53 522 si f 3 x3 3:

line 6-l of Fig. 5;

iron. Fi 'I is a side elevational view of the time Back contact switch (slow make, slow break) Fig. 8 isa vertical sectional view of afront con- The witch shown in Figs. 44 inclusive is a tact switch embodying some of the principles of quick m k l br ak, ba k contact switch, this invention, the switch parts being shown in comprising a, switch envelope 3i (preferably of the position which they take at the instant when 733A glass), through the base of which molyb- 55 the associated coil is deenersized and the disdenum electrodes 32, 33, are pinch-sealed. The 86 electrode 32 is surrounded by a glass insulating sleeve 84 to a point II, where it is iused with a short sleeve 30, of refractory tubing, preferably made oi ceramic material such as Alundum RAM, or M360, inasmuch as this material is readily fusible with Corning 733A glass. The end of the electrode 12 is bare, leaving a contact portion 31 which extends a substantial distance above the top of the sleeve 80, and is adapted to be intermittently placed in electrical contact with the mercury an ll of the switch.

The electrode II is surrounded by a glass sleeve ll until it enters the time delay cup, generally designated ll, and the bated end of the electrode 88 iorms a contact which is constantly immersed in the mercury within the cup is.

The time delay cup ll consists oi an elongated ceramic tube 42 (preierably made from Alundum RAM or M360), the base of which is fused to a glass enlargement or bead l3 associated with the electrodes 32, II. The cup 30 is telescoped over both of the contacts 31, lit, and at some point below the contact I1; the side wall of the cup is reduced in thickness, as indicated at N, by means of a grinding wheel or file, and through this thinned portion of the cup wall a small mercury passage is provided which constitutes the timing element for the switch.

The mercury i'ill is adapted to be raised and lowered between high and low levels by means oi a magnetically responsive displacer N, the

top of which is slightly above the lower pole sleeve 2| when the coil 20 is deenergized. Springs 41, ll. are securedto the top and bottom, respectively, oi the displacer ll to cushion the move ment of the displacer within the envelope, and to clamp guide washers l! in place on the displacer. The upper portion oi the displacer is enlarged to provide greater mass for the displacer, but the interior of the displacer is in free communication with the space on the outside of the displacer through an opening ll, so that the gas till 01' the envelope, which preferably includes both helium and hydrogen, can readily pass through the top of the displacer without impedance.

the lower edge I of the cup.

The 'switch parts in Fig 4 are shown in the position which they take when the coil 16 is deenergized, and it shouldbe noted that the level oi the mercury. w hen the displacer is in its lower position (the high mercury level), is above The upper margin of the cup is inclined, so that when mercuryis displaced to close the circuit through the electrodes I2 and It, the mercurycan enter the cup on the side adjacent to the low point 5|, while the gas in the cup will escape along the opposite side o! the cup. Obviously when the cup 8| is filled with mercury the circuit through the contacts I! and l. is closed. v

when the dis,-.acer I! is raised to the position shown in Fig. 5, the mercury level on the outside oi the cup ll ialls immediately to a position slightly above the passage II, but the column of mercury'within the cup 8| recedes gradually as mercury passes slowly through the restricted passageway ll into the main body of mercury. As soon as the mercury level within the cup falls below the top of the ceramic sleeve 30, the circuit through the contacts l1 and 4| is broken.

Subsequent deenergization of the coil 2! will result in the displacer falling to the position in which it is shown in Fig. 4, and the immediate displacement of mercury by the displacer will cause the cup 3| to become instantaneously flooded with mercury, with the result that the circuit through the contacts 3'! and I is made within a few hundredths of a second after the coil is deenergized.

Front contact switch (quick; make, slow break) The front contact switch shown in Figs. 5-10 inclusive differs but slightly irom the back contact switch of Figs. 4-7 inclusive, the principal difference being that the time delay cup 38 oi the front contact switch is positioned somewhat higher within the envelope and the displacer 52 is oi lighter construction. To the extent that the switch parts are the same. or substantially alike, no description is necessary, and these parts are indicated by like numbers on the drawings.

The displacer 52 comprises an outer sleeve I! of magnetic material, interiorly fitted with a reiractory sleeve 54, preferably oi glass or ceramic material, which projects from both ends of the sleeve 53. The two sleeves are held in desired relative position by the top and bottom springs ll, 48, which are tightly fitted over the projecting ends of the sleeve M, as clearly shown in the drawings.

The air gap between the top and bottom pole pieces 21, 2!, is somewhat lower than the air gap in the back contact switch oi Figs. 4-7 inclusive, and when the coil 25 is energized the displacer is pulled down to the bottom of the switch envelope, as shown in Fig. 9 to immedb ately flood the cup 39 with mercury and substantially instantaneously establish the electrical circuit between the electrodes 82, a. Upon deenergizatlon oi the coil 28, the displacer riserby its buoyancy to the position in which it is shown in Fig. 8, and the mercury level outside 0! the cup I! immediately drops to the level in which it is shown in Fig. 8. As the mercury gradually escapes from the cup I! through the opening II, the mercury level within the cup I! recedes until it falls below the edge 58 of a ceramic cup 51 associated with the contact 31, and as the mercury passes the edge 56 the circuit through the contacts 31 and 40 is broken. The time which it takes ior the mercury to recede from the top of the time delay cup 35 to the edge 53 of the electrode cup 51 represents the time delay factor of the switch. When the mercury has leveled off with the displacer in raised position it is at its low level, as indicated by the line 5|.

Front or back. contact switch (slow make and slow break) It is apparent that by very slight modifications the back and front contact switches shown in Figs. 4-10 inclusive can be easily changed into slow make, slow break switches, l. e., switches in which the time delay action of the restricted mercury passage 45 is utilized on making the circuit through the electrodes, as well as when breaking that circuit. This may be accomplished merely by using a smaller quantity of mercury in the switch, so that when the displacer ll of the back contact switch and the displacer 52 01 the front contact switch are lowered to the positions in which they are shown in Figs. 4 and 9. respectively, the mercury fill .iails to rise above the edge II of the cup I8. although it must rise above the top of the sleeve 3! (Fig. 4) and above the edge 58 of the electrode cup 51 (Fig. 8). By this arrangement the only way mercury is permitted to enter the cup II is through the restricted opening ll, and the distance between the low level of the mercury (i. e., the level of the mercury when the displacer is in its raised position and the mercury is at rest, as indicated by the lines 58 in Figs. 5 and 8), and the lowermost effective point on the'contact 31 (the top of the sleeve 36 in Fig. 4, and the edge 56 of the cup 51 in Fig. 8), determines the time delay characteristics of the switch for the making o! the circuit.

Since the high mercury level, indicated by the line 59 in Figs. 5 and 8, in a slow make, slow break switch of this type (as well as the slightly higher mercury level which is reached at the instant the displacer is lowered) is above the top of the sleeve 36 and the edge 56 of the electrode cup 51, the breaking of the circuit through the electrodes will be delayed by the'retarded drop of the mercury column within the time delay cup 38. In some cases it may be desirable to increase the height of the cup 39 in order to make certain that mercury will not overflow the top of the cup and destroy the timing action of the restricted mercury passage I! when closing the circuit between the electrodes 32 and 33.

Front or back contact switch with retarded make and slow break 1 being closed, and a relatively long time delay when the circuit is being opened. By way 01' example, the switch may have a six second time delay when making the circuit, and a three minute time delay when breaking the circuit, and this particular relationship oftime delays is extremely difilcult to obtain in switches of this type.

The switch shown in Fi'gfili is of'the front contacttype, but it is obvious that the principles of the switch could easily be incorporated in a back'contact switch. To the extent that the switch corresponds with the front contact switch in Figs. 8-10 inclusive, the description will not be repeated, and like reference characters are used on the drawing. The principal diiference between the two switches is that a gas impervious thimble 60,- preferably of glass, is sealed to the electrodes 32; 33, in place oi'the cup 39,

' and the thimble is provided in'its top wall with a 'mercury valve, generally designated iific'ornprising a porous seat 62, pr eferahly of.v coarse ceramic material,- su ch as Alundumjgr'ade RA98, an atelescoping sleeve 83 otrelatively'de'nse ceramic material, such as Alundum ,.gr a'de RAM. The sleeve 83 'andjseat 62 are fused into the top wall of the thimble to form a mercuryyal've cup,

that when the displacer 52 is lowered the mercury'rises above the top of the, thimble a sufficient distance to make certain that a quantity of mercury 64 is in the valve cup 6!. The lower portion of the thimble I8 is provided with .a restricted mercury passage 45, which retards the flow of mercury between the interior and exterior oi the thimble.

' When the switch parts are in the position in which they are shown in Fig. 11, with the mercury at its low level, the circuit through the electrodes is open. Upon lowering the displacer H by the action 01 thecoil 26 (or by deenergizing the coil in the case of a back contact switch), the mercurylevel on the outside of the thimble immediately rises to a level indicated by the line 65, which preferably is above the edge 68 of the sleeve 63 to insure that the mercury valve cup 6| will be filled with mercury. The

.ble 6!! without first ..--the mercury leakage eiementr proportioned mercury within the thimble l0 gradually rises as mercury is permitted to flow into the thimble through the restricted passageway 45, and as soon as the level reaches the edge 50 of the cup 51 the circuit through the electrodes 32, 33, will be closed. The time for the mercury to reach this height depends, of course, upon the size of the opening 45, the diameter of the thimble 60, and certain other factors. The gas entrapped within the thimble ll does not in any way retard the movement of mercury to circuit closing position, because the seat '2 is suiliciently porous to readily pass the gas through the seat and through the mercury globule M in the cup 63 without creating any substantial back pressure.

When the mercury in the switch has leveled oil to its normal high level 81, due to the displacement of the gas in the thimble 60 with mercury, the thimble i0 is completely filled with mercury and subsequent deenergization of the coil, which causes the displacer 52 to rise to its uppermost position, as shown in Figs. 8 and 11, has the re sult of lowering the outside mercury level to the position indicated by the line 88: but the mercury within the thimble Cl is restrained in its downward movement by the slow passage .of-gas through the dense porous sleeve Bland seat 62, the mercury in thevalveji preventing gas from passing through the seat BI-into'the thimthe,electrocle cup fl constltutesthe time delay. interval which characterizes the .breakingxoi' the circuit, and this intervalisfdependent.for its value on the. .density of; the sleeve 63, the diameter and thickness ofthe: orthatsleeve, the diameter'of the thimble filv'thediilerence' in height between the top oftlie 'mercurychamber diiiicult with this arrangementtosobtain time circuitthrough the electrodes of the switch tu It should be n ted that-the ,-restricted mertraversing the dense time in the thimble 80 and the edge-56 ;-ofjthe mer-. ,,.cury cup, and-various other..-factors.. It-iis-not cury passage does netinterferewith the .tizning action of thelsleeve fl, becausethegas time delay element is much slowerin'its 7 Sumn'iarz'l of adi iarll tddsf The switch structureswhichjhave-{bee described have certaininherent advantagesfiand these will be mentioned briefly.

ingand breaking the electricalcircuits.can, be varied between wide limits by Properly choosin action:- than v 1. It is obvious that the time intervals 16mi sappropriate dimensions for the; lilin{ de1ay.chp

39 and the mercury. orifice l,5, 'a nd}by properly positioning the intermittently immersed contact within thefcup 3 9. p i j,

2. Sincethe'functioningof the time delay element is not dependent upon gas densities (with the exception of the modified form shown "in Fig. 11) the switch canibereadily tested during fabrication for its actualtime,delay values with the assurance that the same timedelayvalues will obtain when. theswitch is hermetically sealed oil! at the top, as indicated at 89. For example, it is known that, an .027 drill will .give a six secondtime delayfor a switch of given dimen sions. .Much time and labor is saved in this way and the switch can be produced with a corresponding saving in cost. 

